Papers by Keyword: LiFePO₄/C

Abstract: Li ion battery or LIB is an energy storage device that provides and store electrical energy and chemical energy, respectively. LIBs have been widely developed in the energy sector owing to their considerable high energy density, high capacity, and long-life cycle. In this study, the LiFePO₄/C cathode was synthesized from various precursors FeC₂O₄, FePO₄, Fe₃(PO₄)₂, Fe₂O₃ obtained via co-precipitation method, and continued with solid-state. The effects of precursors were studied in this study. The precursor and the resulting product were analyzed using XRD, FTIR, SEM, and EDX, while the electrochemical performance was tested using charge-discharge, cycle stability and rate capability. All precursors were successfully synthesized as evidenced by XRD, FTIR, SEM, and EDX characterization tests. Based on electrochemical performance test, the highest capacity that can be achieved is 109 mAh/g obtained from LFP with FeC₂O₄ precursor, with a reduction in capacity of 54.7% after 50 cycles.

Abstract: The cathode material LiFePO₄/C composites were synthesized by solid-phase method using cheap and extensive FePO₄ as iron ingredients and glucose as carbon source. The synthesis conditions were studied by changing the calcined temperatures and the ratio of lithium. The results show that the LiFePO₄/C composite synthesized at 600 °C for 10 h exhibits the most homogeneous particle size distribution and excellent electrochemical properties. And it exhibits a specific discharge capacity of 127 mA h/g at 1 C.

Abstract: Synthesis of carbon-coated LiFePO₄ as cathode material is performed through a solid-state process. Materials in the form of a powder comprising LiOH.H₂O and Fe₂O₃ and H₃PO₄ in liquid form are mixed evenly to obtain a homogeneous powder. Through the drying process in an oven with a temperature of 80°C for 24 hours a dry powder is obtained. Powder is subsequently ground and calcined in the horizontal tube furnace at a temperature of 320°C for 10 hours under the flowing nitrogen gas. The obtained powder is further ground and mixed with carbon sources as much as 4wt% of the total powder. Citric acid, tartaric acid and fructose are used as the carbon source. These homogeneously mixed powders are subsequently sintered at a temperature of 800°C for 8 hours under the flowing nitrogen gas. Phase obtained from the solid-state process was analyzed by XRD. Phase composition is analyzed by Rietveld refinement that is included in the GSAS-program. The conductivity of obtained powder as cathode materials is tested by EIS (Electrochemical Impedance Spectroscopy). SEM and BET analysis tests are conducted to determine the morphology of powder which can influence the conductivity of the material.

Abstract: A one-step carbon thermal method was used to prepare LiFePO4/C particles by using normal Fe₂O₃, LiH₂PO₄ and sucrose as raw materials. The effect of H₂ content in the sintering atmosphere of N₂ on the morphology and the electrochemical performance were investigated. LiFePO₄/C materials were characterized by X-ray diffraction, scanning electron microscopy and the elemental analyzer. The results show that the precursor sintering under the atmosphere of 8%H₂+N₂ exhibits the highest electrochemical capacity (162.3 mAh/g at 0.1C) .

Abstract: FePO₄·2H₂O nanoplates are synthesized by a hydrothermal method, using Fe (III) compound as the iron source and are lithiated to LiFePO₄/C by a simple rheological phase mathod. The structure, morphology and electrochemical properties of the FePO₄·2H₂O nanoplates and LiFePO₄/C composites synthesized by changing the concentration of the reactants were characterized in detail by X-ray (XRD), scanning electron microscope (SEM), high-resolution transmission electron microscope and electrochemical measurement. The LiFePO₄/C nanoparticles lithiated from the FePO₄·2H₂O nanoplates when there were about 10 mmol Fe³⁺ in 20 ml water solution demonstrates excellent cyclic performance.

Abstract: LiFePO₄/C was successfully synthesized by one-step solid-state reaction using Fe₂O₃, LiH₂PO₄ and sucrose as raw materials. The effect of synthesis temperature and sintering atmosphere on the electrochemical performance were investigated. LiFePO₄/C materials were characterized by differential scanning calorimetry and thermogravimetry, X-ray diffraction, scanning electron microscopy and XPS. The results show that the synthesis temperature between 750 °C and 800 °C were appropriate and the reductive ambience can enhance the electrochemical performance effectively especially at high rates. The precursor calcined at 750°C for 5h in a N₂+5%H₂ atmosphere exhibited the highest discharge capacity of 155 mAh/g at 0.1C and 141 mAh/g at 1C and showed the best cycle performance.

Abstract: LiFePO4/C composite was synthesized by an easy sol-gel method using FeC2O4•H2O as iron source, citric acid and ethylene glycol as carbon source. The results showed that citric acid was inclined to leave more carbon in the synthesized material than ethylene glycol was and the carbon content increased greatly with the increasing amount of citric acid. When ethylene glycol was applied as carbon source, it left only a few amount of carbon (1.6 wt%) in the material. By optimizing the addition of carbon source, LiFePO4/C particles with uniform carbon coating and a little carbon content was obtained. The LiFePO4/C composite synthesized with 1/1 ratio of ethylene glycol to cations demonstrated the best electrochemical performance with its capacity of 143 mAh/g at 0.1C and 110 mAh/g at 1C within the voltage range of 2.5-4.2V (vs. Li/Li+). The results will provide ideas for the improvement of overall properties of LiFePO4 material for its application in the field of electric vehicles.

Abstract: The LiFe0.98Mn0.02PO4/C was synthesized by spray-drying and low temperature reduction route using FePO4•2H2O as precursor, which was prepared by a simple co-precipitation method. The LiFe0.98Mn0.02PO4/C sample was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and electrochemical measurements. The XRD analysis and SEM images show that sample has the good ordered structure and spherical particle. The charge-discharge tests demonstrate that the powder has the better electrochemical properties, with an initial discharge capacity of 162.1 mAh•g−1 and 155.8 mAh•g−1 at current density of 0.1 C and 1C, respectively. The capacity retention reaches 99.4% after 100 cycles at 1C.

Abstract: The LiFe0.98Ni0.01Nb0.01PO4/C was synthesized by carbon reduction route using FePO4•2H2O as precursor. The LiFe0.98Ni0.01Nb0.01PO4/C sample was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and electrochemical measurements. The XRD analysis, SEM and TEM images show that sample has the good crystal structure, morphology and carbon coating. The charge-discharge tests demonstrate that the powder has the better electrochemical properties, with an initial discharge capacity of 164.6 mAh•g−1 at current density of 0.1 C. The capacity retention reaches 99.8% after 100 cycles at 0.1C.

Abstract: To improve the electrochemical performance of LiFePO₄, LiFePO₄/C composite materials were prepared by solid-state synthesis method with Fe₂O₃ as one of the starting materials. The phase composition, microstructure and morphology of samples were determined by X-ray diffraction (XRD) and scanning electron microscope (SEM). The electrochemical performance of samples were characterized by constant current charge-discharge method. The results show that the prepared samples have the single phase, and the carbon coating lead to no change of the crystal structure of LiFePO₄. The sample with carbon content of 10wt% shows the best electrochemical properties. Its initial discharge capacity is 144.6 mA·h /g at 0.2C rate. After 30 cycles the capacity remains 131.4 mA·h /g, and the capacity retention rate is 91%.